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EP-3497458-B1 - MAGNETIC FIELD DEVICE FOR MRI/NMR AND METHOD OF PROVIDING THE DEVICE

EP3497458B1EP 3497458 B1EP3497458 B1EP 3497458B1EP-3497458-B1

Inventors

  • RAPOPORT, URI
  • GOLDFARB, YAIR
  • COHEN, YORAM

Dates

Publication Date
20260506
Application Date
20170326

Claims (12)

  1. A magnetic field device (100, 200) for performing magnetic field analysis of an object positioned within a gap of the device (100, 200) by using magnetic resonance imaging or nuclear magnetic resonance, the device (100, 200) comprising: a first magnet (101, 201, 401); a first ferromagnetic element (102, 202) positioned adjacent to the first magnet (101, 201, 401); a second magnet (121, 221); a second ferromagnetic element (122, 222) positioned adjacent to the second magnet (121, 221) and relative to the first ferromagnetic element (102, 202) to create the gap (150, 250, 450) between the first ferromagnetic element (102, 202) and the second ferromagnetic element (122, 222); a third magnet (130, 230, 430, 440); a shell (111,112) positioned at a predetermined distance from the first magnet (101, 201, 401) and the second magnet (121, 221), to at least partially envelop the first magnet (101, 201, 401) and the second magnet (121, 221); a fourth magnet (103, 203) positioned around the first magnet (101, 201, 401); and a fifth magnet (123, 223) positioned around the second magnet (121,221), wherein: the predetermined distance is based on a desired magnetic field strength in the gap (150, 250, 450), a thickness of the shell (111,112) corresponds to the predetermined distance, the first magnet (101, 201, 401) and the second magnet (122, 222) have the same magnetization direction along a first axis, the fourth magnet (103, 203) and the fifth magnet (123, 223) each have a magnetization direction perpendicular to the magnetization direction of the first magnet (101, 201, 401) along a second axis perpendicular to the first axis, wherein the fourth magnet (103, 203) has a magnetization direction away from the first magnet (101, 201, 401) and the fifth magnet (123, 223) has a magnetization direction towards the second magnet (122, 222), and the third magnet (130, 230, 430, 440) has a magnetization direction which is opposite to the magnetization direction of the first and second magnets (201,221) along the first axis, characterised in that the third magnet (130, 230, 430, 440) is positioned between the first ferromagnetic element (102, 202) and the second ferromagnetic element (122, 222), and the third magnet (130, 230, 430, 440) being within the gap (150, 250, 450).
  2. The magnetic field device (100, 200) of claim 1, wherein the shell (111,112) at least partially envelops the first ferromagnetic element (102, 202) and second ferromagnetic element (122, 222).
  3. The magnetic field device (100, 200) of claim 1, further including one or more additional third magnets (130, 230, 430, 440).
  4. The magnetic field device (100, 200) of claim 1, wherein the thickness of the shell (111,112) is inversely proportional to the distance.
  5. The magnetic field device (100, 200) of claim 4, wherein the thickness of the shell (111,112) is based on the distance exceeding a predetermined threshold.
  6. The magnetic field device (100, 200) of claim 1, wherein the distance is also based on the weight of the at least one magnet.
  7. The magnetic field device (100, 200) of claim 1, wherein at least one of the first magnet (101, 201, 401), the second magnet (121, 221) and the third magnet (130, 230, 430) is a permanent magnet, a superconducting magnet, a resistive magnet, or any combination thereof.
  8. The magnetic field device (100, 200) of claim 1, wherein the first magnet (101, 201, 401), the second magnet (121, 221), the third magnet (130, 230, 430), and the shell (111,112) have dimensions that are based on the desired magnetic field strength, a type of object to be imaged, or any combination thereof.
  9. The magnetic field device (100, 200) of claim 1, wherein the shell (111,112) comprises a metal alloy.
  10. The magnetic field device (100, 200) of claim 1, wherein the distance is 50 millimeters.
  11. A method of directing magnetic fields into a measurement volume, the method comprising: providing a magnetic field device (100, 200) according to any preceding claim; generating, using the first magnet (101, 201, 401), a first magnetic field in a first direction with a first magnetic field strength; distributing, using the first ferromagnetic element (102, 202), the first magnetic field into the measurement volume to create a substantially uniform magnetic flux; generating, using the second magnet (121, 221), a second magnetic field in the first direction with a second magnetic field strength; distributing, using the second ferromagnetic element (122, 222), the second magnetic field into the measurement volume to create a substantially uniform magnetic flux; increasing the strength of the magnetic field in the measurement volume by generating, using the third magnet (130, 230, 430, 440), a third magnetic field with a third magnetic field strength and directing the third magnetic field in a second direction parallel and substantially opposite to the first direction.
  12. The method of claim 11, further comprising: positioning an object within the measurement volume; and performing magnetic field analysis on the object.

Description

FIELD OF THE INVENTION Generally, the present invention relates to magnetic devices. More particularly, the present invention relates to devices, systems and methods for obtaining magnetic measurements. BACKGROUND OF THE INVENTION Electromagnetic based instruments can be used for measuring properties of matter and/or used for identifying its composition. For example, an electromagnetic based instrument capable of performing magnetic resonance spectroscopy can be used to obtain physical, chemical and/or structural information about matter (e.g., a molecule). Typically, in order to perform magnetic resonance spectroscopy, for example to provide high quality measurements of an object/subject (e.g., high resolution image and/or image contrast), it can be desirable for the magnetic field inside of a zone of measurement (e.g., an area where an object is to be measured is positioned) to be substantially stable and/or uniform. Other applications (e.g., magnetic resonance imaging (MRI)) can also require a high, stable, and/or uniform magnetic field strength. Some systems that use magnetic fields for measurements can include magnetic coils to create the magnetic fields, with application of current to the coil, while other systems can utilize permanent magnets to create the magnetic fields, which typically do not require application of a current. One difficulty in creating a magnetic field in a zone of measurement with permanent magnet(s) that is sufficient for magnetic resonance spectroscopy and/or magnetic imaging (e.g., that is substantially stable and/or uniform) is that magnetic fields produced by the permanent magnets(s) can be non-homogeneous, thus typically resulting in a non-homogenous magnetic field within the zone of measurement. Some current solutions for creating a homogenous and/or stable magnetic field within a zone of measurement using a permanent magnet can include adding additional elements to an imaging device (e.g., coils) and/or increasing the size of the permanent magnets. One difficulty with current solutions is that as the number of elements in a magnetic measurement device increases and/or the size of the permanent magnets increases, the weight, size and/or cost of the device can increase. Another difficulty with current solutions is that a magnetic measurement device that is heavy can cause a lack of mobility. For example, for magnetic measurement devices in a hospital setting (e.g., magnetic resonance imaging (MRI) devices), a heavy and/or large device can prevent hospital personnel from moving an MRI. This can cause further difficulties, when imaging patients that can be hard to move (e.g., patients that are hooked up to multiple life support and/or monitoring equipment). In another example, for magnetic measurement devices in an industrial setting (e.g., nuclear magnetic measurement (NMR) devices that measure properties of fluids and/or drilling muds in oil production facilities), a heavy and/or large device can prevent personnel from measuring the fluids/muds at various locations in the processes. Therefore it can be desirable to achieve a desired magnetic field strength, having sufficient homogeneity and/or stability, and/or reducing a total weight of a magnetic measurement system. US4937545A discloses a system of permanent magnets having a permeable magnetic yoke formed by two opposite support walls and connected by two connecting walls, two main permanent magnets of the same magnetization direction disposed on the support walls within the yoke and whereof the facing surfaces carry opposite poles, two permeable magnetic plates on the facing surfaces and which define an air gap and two lateral permanent magnets whose magnetization direction is opposite to that of the main permanent magnets and which also define the air gap, being positioned facing the connecting walls and within the yoke, characterized in that the lateral permanent magnets extend laterally between the permeable magnetic plates, so as to be positioned facing the lateral edges of the main permanent magnets and the permeable magnetic plates. JP2004113455A discloses a device which seeks to provide a magnetic field generating device capable of enhancing the intensity of a center magnetic field by suppressing a leak magnetic field while suppressing an increase in the weight of the device itself. This magnetic field generating device includes a device body formed into an annular shape using a plurality of permanent magnets so as to have a magnetic field generating space. Shield members with a thickness of 5 - 35 mm are provided to the outer periphery of the device body so as to be separated from the surfaces of the permanent magnets by 0 - 35 mm. The shield members have a saturated magnification of 1.5T or more. Insertion members with a saturated magnification of 0.2T or less are provided between the permanent magnets and the shield members. JPS62139304A discloses a device which seeks to make the lines of magnetic force uniform